Fundamental Investigation On Single Photon Detection

Single photon detection is one of the key technologies to realize quantum optical communication. Based on the core components of single photon detection:the avalanche photodiode (APD) and photomultiplier tube (PMT), we conducted a thorough research in refrigeration, photon counting and photon interference. The following are our research and conclusions:Firstly, we successfully developed a refrigerating device of infrared single-photon detection system, which can apply to InGaAs/InP-APD very well. Reducing the temperature by semiconductor refrigeration piece of4level and combined with vacuum device which can reduce heat exchange, this refrigerating device can reduce the working temperature of APD to -44.5℃degrees Celsius. By using this device, we achieved the volt-ampere characteristic of InGaAs APD module (model:APD050A) at low temperature. The results showed that the avalanche voltage of the APD is28.5V in-40℃.Secondly, we measured a series important parameters of PMT (model:CR105) in detail, including cathode and anode volt-ampere characteristics and the transit time. The transit time is measured about76.6ns. In further research, we achieved the pulse height distribution (PHD) of PMT by using photon counting method. PHD fully indicated the amplitude relationship between noise and optical signal, which is of important value to realize high precision single photon detection. Furthermore, by analyzing the result of PHD, selecting screening level, and doing a lot of counting statistics, we achieved the photon Poisson distribution of extremely weak light at5pW.On the basis of the above work, we successfully conducted optical coherence measurement based on optical pulses interference. By using a feedback-stabilized fiber Mach-Zehnder interferometer (MZI) with a PZT-based phase shifter, laser coherence length is successfully measured by the method of optical pulses interference. Our scheme can measure not only the high-coherence laser but also low-coherence pulses, which laid the foundation for the further research of quantum interference.